1. Field of the Invention
The present invention relates to a sliding track assembly and more particularly, to such a sliding track assembly, which uses two torsional spring members to join a sliding member to a track member for allowing stable sliding movement of the sliding member relative to the track member.
2. Description of the Related Art
Sliding track assemblies are intensively used in different products around us. For example, a sliding track assembly allows a drawer to be moved in and out of a cabinet. Instead of the use of a hinge in a lifting cover type cell phone, a sliding track assembly may be used in a cell phone for allowing the sliding cover of the cell phone to be moved in and out of the mainframe of the cell phone between the open position and the close position. When the sliding cover is extended out, the operating face panel of the cell phone is exposed to the outside for operation. When the sliding cover is moved to the received (close) position, it keeps the operating face panel of the cell phone from sight.
Taiwan Patent Publication No. M252209, entitled “Sliding Cover Device”, teaches the application of a sliding track assembly. According to this design, the sliding cover device (sliding track assembly) comprises a bottom plate, which has two sliding rails and a plurality of mounting through holes at two sides, and a top cover, which has a plurality of mounting through holes and two sliding grooves respectively coupled to the sliding rails, and a spring member, which has one end pivoted to one side of the bottom plate and the other end pivoted to the corresponding side of the top cover. Because this design uses only one single spring member and has the spring member coupled between the bottom plate and the top cover at one lateral side, the spring member does not hold the top cover in balance, i.e., the force of the spring member holds one lateral side of the top cover in close contact with the bottom plate and a gap is left between the other lateral side of the top cover and the corresponding lateral side of the bottom plate. Therefore, the top cover may vibrate when it is moved relative to the bottom plate.
In the specification of the cited Taiwan Patent, a prior art dual-spring type sliding cover structure is cited to have the drawback that the spring members tend to be broken or permanently deformed due to a thin diameter of the spring wires. Theoretically, the use of two spring members can keep the sliding cover is balance when the sliding cover is moved relative to the bottom plate. However, according to the cited prior art dual-spring type sliding cover structure, the two spring members each have a fixed end respectively fastened to a respective locating hole on the middle of the bottom plate. However, because the two locating holes of the bottom plate are arranged at different elevations and in a parallel manner relative to the sliding rails, the fixed ends of the two spring members are not aligned in line when the top cover is moved relative to the bottom plate to the dead point. At this time, a shearing force is produced, resulting in vibration of the top cover relative to the bottom plate.